Adenoviridae
Encyclopedia
Adenoviruses are medium-sized (90–100 nm), nonenveloped (without an outer lipid bilayer) icosahedral virus
es composed of a nucleocapsid and a double-stranded linear DNA
genome. There are 57 described serotype
s in humans, which are responsible for 5–10% of upper respiratory infections in children, and many infections in adults as well.
Virus
es of the family
Adenoviridae infect various species of vertebrates, including humans. Adenoviruses were first isolated in 1953 from human adenoid
s. They are classified as group I under the Baltimore classification
scheme, meaning their genomes consist of double stranded DNA.
:
In humans, there are 57 accepted human adenovirus types (HAdV-1 to 57) in seven species (Human adenovirus A to G):
Different types/serotypes are associated with different conditions:
When not restricting the subject to human viruses, Adenoviridae can be divided into five genera: Mastadenovirus, Aviadenovirus, Atadenovirus
, Siadenovirus, and Ichtadenovirus.
associated with each penton base of the capsid
(see picture below) that aids in attachment to the host cell via the coxsackie-adenovirus receptor on the surface of the host
cell
.
In 2010, scientists announced that they had solved the structure of the human adenovirus at the atomic level, making the largest high-resolution model ever. The virus is composed of around 1 million amino acid residues and weighs around 150 MDa
.
. Although this is significantly larger than other viruses in its Baltimore group
, it is still a very simple virus and is heavily reliant on the host cell for survival and replication. An interesting feature of this viral genome is that it has a terminal 55 kDa
protein associated with each of the 5' ends of the linear dsDNA. These are used as primers in viral replication and ensure that the ends of the virus' linear genome are adequately replicated.
and are able to replicate
in the nucleus
of mammal
ian cells using the host’s replication machinery.
Entry of adenoviruses into the host cell involves two sets of interactions between the virus and the host cell. Most of the action occurs at the vertices. Entry into the host cell is initiated by the knob domain
of the fiber protein binding to the cell receptor. The two currently established receptors are: CD46
for the group B human adenovirus serotypes and the coxsackievirus adenovirus receptor (CAR) for all other serotypes. There are some reports suggesting MHC
molecules and sialic acid
residues functioning in this capacity as well. This is followed by a secondary interaction, where a specialized motif in the penton base protein interacts with an integrin
molecule. It is the co-receptor interaction that stimulates internalization of the adenovirus. This co-receptor molecule is αv integrin
. Binding to αv integrin results in endocytosis
of the virus particle via clathrin-coated
pits. Attachment to αv integrin stimulates cell signaling and thus induces actin
polymerization resulting in entry of the virion into the host cell within an endosome
.
Once the virus has successfully gained entry into the host cell, the endosome acidifies, which alters virus topology by causing capsid components to disassociate. These changes as well as the toxic nature of the pentons result in the release of the virion into the cytoplasm. With the help of cellular microtubules, the virus is transported to the nuclear pore complex, whereby the adenovirus particle disassembles. Viral DNA is subsequently released, which can enter the nucleus
via the nuclear pore
. After this the DNA associates with histone
molecules. Thus, viral gene expression can occur and new virus particles can be generated.
The adenovirus life cycle
is separated by the DNA replication
process into two phases: an early and a late phase. In both phases, a primary transcript
that is alternatively spliced
to generate monocistronic mRNAs compatible with the host’s ribosome
is generated, allowing for the products to be translated
.
The early genes are responsible for expressing mainly non-structural, regulatory proteins. The goal of these proteins is threefold: to alter the expression of host proteins that are necessary for DNA synthesis
; to activate other virus genes (such as the virus-encoded DNA polymerase
); and to avoid premature death of the infected cell by the host-immune defenses (blockage of apoptosis
, blockage of interferon
activity, and blockage of MHC class I
translocation and expression).
Some adenoviruses under specialized conditions can transform cells using their early gene products. E1a (binds Retinoblastoma tumor suppressor protein
) has been found to immortalize primary cells in vitro allowing E1b (binds p53
tumor suppressor) to assist and stably transform the cells. Nevertheless, they are reliant upon each other to successfully transform the host cell and form tumors.
DNA replication separates the early and late phases. Once the early genes have liberated adequate virus proteins, replication machinery, and replication substrates, replication of the adenovirus genome can occur. A terminal protein that is covalently bound to the 5’ end of the adenovirus genome acts as a primer
for replication. The viral DNA polymerase then uses a strand displacement mechanism, as opposed to the conventional Okazaki fragments used in mammalian DNA replication, to replicate the genome.
The late phase of the adenovirus lifecycle is focused on producing sufficient quantities of structural protein to pack all the genetic material produced by DNA replication. Once the viral components have successfully been replicated, the virus is assembled into its protein shells and released from the cell as a result of virally induced cell lysis
.
conditions, allowing for prolonged survival outside of the body and water. Adenoviruses are spread primarily via respiratory droplets, however they can also be spread by fecal routes as well.
.
adenoviruses are well known, type 1 and 2. Type 1 causes infectious canine hepatitis
, a potentially fatal disease involving vasculitis
and hepatitis
. Type 1 infection can also cause respiratory and eye infections. Canine adenovirus 2 (CAdV-2) is one of the potential causes of kennel cough
. Core vaccine
s for dog
s include attenuated live CAdV-2, which produces immunity to CAdV-1 and CAdV-2. CAdV-1 was initially used in a vaccine for dogs, but cornea
l edema
was a common complication.
Adenovirus in Reptiles
is poorly understood, but research is currently in progress.
Adenoviruses are also known to cause respiratory infections in horse
s, cattle
, pig
s, sheep, and goat
s. Equine adenovirus 1 can also cause fatal disease in immunocompromised Arabian foal
s, involving pneumonia and destruction of pancreatic
and salivary gland
tissue.
The U.S. Army Medical Research and Materiel Command announced on 31 October 2011 that the new adenovirus vaccine, which replaces the older version that has been out of production for over a decade, was shipped to basic training sites Oct. 18, 2011. More information is available here.
Good hygiene, including handwashing, is still the best way to avoid picking up the adenovirus from an infected person.
, tonsilitis (which may look exactly like strep throat
and cannot be distinguished from strep except by throat culture), an ear infection
, or croup
. Adenoviruses can also cause gastroenteritis
(stomach flu). A combination of conjunctivitis and tonsilitis is particularly common with adenovirus infections. Some children (especially small ones) can develop adenovirus bronchiolitis
or pneumonia
, both of which can be severe. In babies, adenoviruses can also cause coughing fits that look almost exactly like whooping cough. Adenoviruses can also cause viral meningitis
or encephalitis
. Rarely, adenovirus can cause hemorrhagic cystitis
(inflammation of the urinary bladder—a form of urinary tract infection
— with blood in the urine).
Most people recover from adenovirus infections by themselves, but people with immunodeficiency
sometimes die of adenovirus infections, and — rarely — even previously healthy people can die of these infections.
Adenoviruses are often transmitted by expectorate, but can also be transmitted by contact with an infected person, or by virus particles left on objects such as towels and faucet handles. Some people with adenovirus gastroenteritis may shed the virus in their stools for months after getting over the symptoms. The virus can be passed from one person to another through some sexual practices, and through water in swimming pools that do not have enough chlorine in them. As with many other illnesses, good handwashing is one way to lessen the spread of adenoviruses from one person to another. Heat and bleach
will kill adenoviruses on objects.
, in the form of recombinant DNA
or protein. Specific modifications on fibre proteins are used to target Adenovirus to certain cell types; a major effort is made to limit hepatotoxicity
and prevent multiple organ failure. Adenovirus dodecahedron can qualify as a potent delivery platform for foreign antigens to human myeloid dendritic cells (MDC), and that it is efficiently presented by MDC to M1-specific CD8+ T lymphocytes.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es composed of a nucleocapsid and a double-stranded linear DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
genome. There are 57 described serotype
Serotype
Serotype or serovar refers to distinct variations within a subspecies of bacteria or viruses. These microorganisms, viruses, or cells are classified together based on their cell surface antigens...
s in humans, which are responsible for 5–10% of upper respiratory infections in children, and many infections in adults as well.
Virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Adenoviridae infect various species of vertebrates, including humans. Adenoviruses were first isolated in 1953 from human adenoid
Adenoid
Adenoids are a mass of lymphoid tissue situated posterior to the nasal cavity, in the roof of the nasopharynx, where the nose blends into the throat....
s. They are classified as group I under the Baltimore classification
Baltimore classification
The Baltimore classification, developed by David Baltimore, is a virus classification system that groups viruses into families, depending on their type of genome and their method of replication....
scheme, meaning their genomes consist of double stranded DNA.
Classification
This family contains the following generaGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
:
- Genus AtadenovirusAtadenovirusAtadenoviruses infect animals with a broad host range from several vertebrate classes .-Types of Atadenovirus:Referenced from *Bovine adenovirus D**Bovine adenovirus 4**Bovine adenovirus 5**Bovine adenovirus 8...
; type species: Ovine adenovirus D - Genus Aviadenovirus; type species: Fowl adenovirus A
- Genus Ichtadenovirus; type species: Sturgeon adenovirus A
- Genus Mastadenovirus; type species: Human adenovirus C; others include AD-36
- Genus Siadenovirus; type species: Frog adenovirus
Diversity
Classification of Adenoviridae can be complex.In humans, there are 57 accepted human adenovirus types (HAdV-1 to 57) in seven species (Human adenovirus A to G):
- A: 12, 18, 31
- B: 3, 7, 11, 14Adenovirus serotype 14Adenovirus serotype 14 is a serovar of adenovirus which, unlike other adenovirus serovars, is known to cause potentially fatal adenovirus infections...
, 16, 21, 34, 35, 50, 55 - C: 1, 2, 5, 6, 57
- D: 8, 9, 10, 13, 15, 17, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 33, 36, 37, 38, 39, 42, 43, 44, 45, 46, 47, 48, 49, 51, 53, 54, 56
- E: 4
- F: 40, 41
- G: 52
Different types/serotypes are associated with different conditions:
- respiratory diseaseRespiratory diseaseRespiratory disease is a medical term that encompasses pathological conditions affecting the organs and tissues that make gas exchange possible in higher organisms, and includes conditions of the upper respiratory tract, trachea, bronchi, bronchioles, alveoli, pleura and pleural cavity, and the...
(mainly species HAdV-B and C) - conjunctivitisConjunctivitisConjunctivitis refers to inflammation of the conjunctiva...
(HAdV-B and D) - gastroenteritisGastroenteritisGastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
(HAdV-F types 40, 41, HAdV-G type 52)
When not restricting the subject to human viruses, Adenoviridae can be divided into five genera: Mastadenovirus, Aviadenovirus, Atadenovirus
Atadenovirus
Atadenoviruses infect animals with a broad host range from several vertebrate classes .-Types of Atadenovirus:Referenced from *Bovine adenovirus D**Bovine adenovirus 4**Bovine adenovirus 5**Bovine adenovirus 8...
, Siadenovirus, and Ichtadenovirus.
Structure
Adenoviruses represent the largest nonenveloped viruses. Because of their large size, they are able to be transported through the endosome (i.e., envelope fusion is not necessary). The virion also has a unique "spike" or fiberFiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....
associated with each penton base of the capsid
Capsid
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...
(see picture below) that aids in attachment to the host cell via the coxsackie-adenovirus receptor on the surface of the host
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
.
In 2010, scientists announced that they had solved the structure of the human adenovirus at the atomic level, making the largest high-resolution model ever. The virus is composed of around 1 million amino acid residues and weighs around 150 MDa
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
.
Genome
The adenovirus genome is linear, non-segmented double-stranded (ds) DNA that is between 26 and 45 Kbp. This allows the virus to theoretically carry 22 to 40 genesGênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
. Although this is significantly larger than other viruses in its Baltimore group
Baltimore classification
The Baltimore classification, developed by David Baltimore, is a virus classification system that groups viruses into families, depending on their type of genome and their method of replication....
, it is still a very simple virus and is heavily reliant on the host cell for survival and replication. An interesting feature of this viral genome is that it has a terminal 55 kDa
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
protein associated with each of the 5' ends of the linear dsDNA. These are used as primers in viral replication and ensure that the ends of the virus' linear genome are adequately replicated.
Replication
Adenoviruses possess a linear dsDNA genomeGenome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
and are able to replicate
Self-replication
Self-replication is any behavior of a dynamical system that yields construction of an identical copy of that dynamical system. Biological cells, given suitable environments, reproduce by cell division. During cell division, DNA is replicated and can be transmitted to offspring during reproduction...
in the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian cells using the host’s replication machinery.
Entry of adenoviruses into the host cell involves two sets of interactions between the virus and the host cell. Most of the action occurs at the vertices. Entry into the host cell is initiated by the knob domain
Protein domain
A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...
of the fiber protein binding to the cell receptor. The two currently established receptors are: CD46
CD46
CD46 complement regulatory protein also known as CD46 and Membrane Cofactor Protein is a protein which in humans is encoded by the CD46 gene. CD46 is an inhibitory complement receptor.- Gene :...
for the group B human adenovirus serotypes and the coxsackievirus adenovirus receptor (CAR) for all other serotypes. There are some reports suggesting MHC
Major histocompatibility complex
Major histocompatibility complex is a cell surface molecule encoded by a large gene family in all vertebrates. MHC molecules mediate interactions of leukocytes, also called white blood cells , which are immune cells, with other leukocytes or body cells...
molecules and sialic acid
Sialic acid
Sialic acid is a generic term for the N- or O-substituted derivatives of neuraminic acid, a monosaccharide with a nine-carbon backbone. It is also the name for the most common member of this group, N-acetylneuraminic acid...
residues functioning in this capacity as well. This is followed by a secondary interaction, where a specialized motif in the penton base protein interacts with an integrin
Integrin
Integrins are receptors that mediate attachment between a cell and the tissues surrounding it, which may be other cells or the ECM. They also play a role in cell signaling and thereby regulate cellular shape, motility, and the cell cycle....
molecule. It is the co-receptor interaction that stimulates internalization of the adenovirus. This co-receptor molecule is αv integrin
ITGAV
Integrin alpha-V is a protein that in humans is encoded by the ITGAV gene.-Further reading:-External links:* Info with links in the...
. Binding to αv integrin results in endocytosis
Endocytosis
Endocytosis is a process by which cells absorb molecules by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane...
of the virus particle via clathrin-coated
Clathrin
Clathrin is a protein that plays a major role in the formation of coated vesicles. Clathrin was first isolated and named by Barbara Pearse in 1975. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When the triskelia interact they form a polyhedral lattice...
pits. Attachment to αv integrin stimulates cell signaling and thus induces actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
polymerization resulting in entry of the virion into the host cell within an endosome
Endosome
In biology, an endosome is a membrane-bound compartment inside eukaryotic cells. It is a compartment of the endocytic membrane transport pathway from the plasma membrane to the lysosome. Molecules internalized from the plasma membrane can follow this pathway all the way to lysosomes for...
.
Once the virus has successfully gained entry into the host cell, the endosome acidifies, which alters virus topology by causing capsid components to disassociate. These changes as well as the toxic nature of the pentons result in the release of the virion into the cytoplasm. With the help of cellular microtubules, the virus is transported to the nuclear pore complex, whereby the adenovirus particle disassembles. Viral DNA is subsequently released, which can enter the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
via the nuclear pore
Nuclear pore
Nuclear pores are large protein complexes that cross the nuclear envelope, which is the double membrane surrounding the eukaryotic cell nucleus. There are about on average 2000 nuclear pore complexes in the nuclear envelope of a vertebrate cell, but it varies depending on cell type and the stage in...
. After this the DNA associates with histone
Histone
In biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...
molecules. Thus, viral gene expression can occur and new virus particles can be generated.
The adenovirus life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
is separated by the DNA replication
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
process into two phases: an early and a late phase. In both phases, a primary transcript
Primary transcript
A primary transcript is an RNA molecule that has not yet undergone any modification after its synthesis. For example, a precursor messenger RNA is a primary transcript that becomes a messenger RNA after processing, and a primary microRNA precursor becomes a microRNA after processing....
that is alternatively spliced
Alternative splicing
Alternative splicing is a process by which the exons of the RNA produced by transcription of a gene are reconnected in multiple ways during RNA splicing...
to generate monocistronic mRNAs compatible with the host’s ribosome
Ribosome
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....
is generated, allowing for the products to be translated
Translation (genetics)
In molecular biology and genetics, translation is the third stage of protein biosynthesis . In translation, messenger RNA produced by transcription is decoded by the ribosome to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein...
.
The early genes are responsible for expressing mainly non-structural, regulatory proteins. The goal of these proteins is threefold: to alter the expression of host proteins that are necessary for DNA synthesis
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
; to activate other virus genes (such as the virus-encoded DNA polymerase
DNA polymerase
A DNA polymerase is an enzyme that helps catalyze in the polymerization of deoxyribonucleotides into a DNA strand. DNA polymerases are best known for their feedback role in DNA replication, in which the polymerase "reads" an intact DNA strand as a template and uses it to synthesize the new strand....
); and to avoid premature death of the infected cell by the host-immune defenses (blockage of apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
, blockage of interferon
Interferon
Interferons are proteins made and released by host cells in response to the presence of pathogens—such as viruses, bacteria, or parasites—or tumor cells. They allow communication between cells to trigger the protective defenses of the immune system that eradicate pathogens or tumors.IFNs belong to...
activity, and blockage of MHC class I
MHC class I
MHC class I molecules are one of two primary classes of major histocompatibility complex molecules and are found on every nucleated cell of the body...
translocation and expression).
Some adenoviruses under specialized conditions can transform cells using their early gene products. E1a (binds Retinoblastoma tumor suppressor protein
Retinoblastoma protein
The retinoblastoma protein is a tumor suppressor protein that is dysfunctional in the majority types of cancer. One highly studied function of pRb is to prevent excessive cell growth by inhibiting cell cycle progression until a cell is ready to divide...
) has been found to immortalize primary cells in vitro allowing E1b (binds p53
P53
p53 , is a tumor suppressor protein that in humans is encoded by the TP53 gene. p53 is crucial in multicellular organisms, where it regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer...
tumor suppressor) to assist and stably transform the cells. Nevertheless, they are reliant upon each other to successfully transform the host cell and form tumors.
DNA replication separates the early and late phases. Once the early genes have liberated adequate virus proteins, replication machinery, and replication substrates, replication of the adenovirus genome can occur. A terminal protein that is covalently bound to the 5’ end of the adenovirus genome acts as a primer
Primer (molecular biology)
A primer is a strand of nucleic acid that serves as a starting point for DNA synthesis. They are required for DNA replication because the enzymes that catalyze this process, DNA polymerases, can only add new nucleotides to an existing strand of DNA...
for replication. The viral DNA polymerase then uses a strand displacement mechanism, as opposed to the conventional Okazaki fragments used in mammalian DNA replication, to replicate the genome.
The late phase of the adenovirus lifecycle is focused on producing sufficient quantities of structural protein to pack all the genetic material produced by DNA replication. Once the viral components have successfully been replicated, the virus is assembled into its protein shells and released from the cell as a result of virally induced cell lysis
Lysis
Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....
.
Transmission
Adenoviruses are unusually stable to chemical or physical agents and adverse pHPH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
conditions, allowing for prolonged survival outside of the body and water. Adenoviruses are spread primarily via respiratory droplets, however they can also be spread by fecal routes as well.
Humans
Humans infected with adenoviruses display a wide range of responses, from no symptoms at all to the severe infections typical of Adenovirus serotype 14Adenovirus serotype 14
Adenovirus serotype 14 is a serovar of adenovirus which, unlike other adenovirus serovars, is known to cause potentially fatal adenovirus infections...
.
Animals
Two types of canineCanidae
Canidae is the biological family of carnivorous and omnivorous mammals that includes wolves, foxes, jackals, coyotes, and domestic dogs. A member of this family is called a canid . The Canidae family is divided into two tribes: Canini and Vulpini...
adenoviruses are well known, type 1 and 2. Type 1 causes infectious canine hepatitis
Infectious canine hepatitis
Infectious canine hepatitis is an acute liver infection in dogs caused by canine adenovirus type-1 . CAV-1 also causes disease in wolves, coyotes, and bears, and encephalitis in foxes. The virus is spread in the feces, urine, blood, saliva, and nasal discharge of infected dogs. It is contracted...
, a potentially fatal disease involving vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
and hepatitis
Hepatitis
Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"...
. Type 1 infection can also cause respiratory and eye infections. Canine adenovirus 2 (CAdV-2) is one of the potential causes of kennel cough
Kennel cough
Kennel cough is a highly contagious canine illness characterized by inflammation of the upper respiratory system. It can be caused by viral infections such as canine distemper, canine adenovirus, canine parainfluenza virus, or canine respiratory coronavirus, or bacterial infections such as...
. Core vaccine
Vaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
s for dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s include attenuated live CAdV-2, which produces immunity to CAdV-1 and CAdV-2. CAdV-1 was initially used in a vaccine for dogs, but cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
l edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
was a common complication.
Adenovirus in Reptiles
Agamid adenovirus
Agamid adenovirus is a type of virus in the Adenoviridae family. The virus is widespread in captive populations of Pogona vitticeps, known commonly as the Inland Bearded Dragon, in the United States. Other countries with confirmed cases are Australia, Japan, Germany, The Netherlands, Belgium, UK...
is poorly understood, but research is currently in progress.
Adenoviruses are also known to cause respiratory infections in horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s, cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
, pig
Pig
A pig is any of the animals in the genus Sus, within the Suidae family of even-toed ungulates. Pigs include the domestic pig, its ancestor the wild boar, and several other wild relatives...
s, sheep, and goat
Goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s. Equine adenovirus 1 can also cause fatal disease in immunocompromised Arabian foal
Arabian horse
The Arabian or Arab horse is a breed of horse that originated on the Arabian Peninsula. With a distinctive head shape and high tail carriage, the Arabian is one of the most easily recognizable horse breeds in the world. It is also one of the oldest breeds, with archaeological evidence of horses...
s, involving pneumonia and destruction of pancreatic
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...
and salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...
tissue.
Prevention
In the past, US military recruits were vaccinated against two serotypes of adenotypes, with a corresponding decrease in illnesses caused by those serotypes. The vaccine is no longer manufactured, and there are currently no vaccines available to protect against the adenovirus.The U.S. Army Medical Research and Materiel Command announced on 31 October 2011 that the new adenovirus vaccine, which replaces the older version that has been out of production for over a decade, was shipped to basic training sites Oct. 18, 2011. More information is available here.
Good hygiene, including handwashing, is still the best way to avoid picking up the adenovirus from an infected person.
Infections
Most infections with adenovirus result in infections of the upper respiratory tract. Adenovirus infections often show up as conjunctivitisConjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...
, tonsilitis (which may look exactly like strep throat
Strep throat
Streptococcal pharyngitis, streptococcal tonsillitis, or streptococcal sore throat is a type of pharyngitis caused by a group A streptococcal infection. It affects the pharynx including the tonsils and possibly the larynx. Common symptoms include fever, sore throat, and enlarged lymph nodes...
and cannot be distinguished from strep except by throat culture), an ear infection
Otitis media
Otitis media is inflammation of the middle ear, or a middle ear infection.It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two categories of ear inflammation that can underlie what is commonly called an earache,...
, or croup
Croup
Croup is a respiratory condition that is usually triggered by an acute viral infection of the upper airway. The infection leads to swelling inside the throat, which interferes with normal breathing and produces the classical symptoms of a "barking" cough, stridor, and hoarseness...
. Adenoviruses can also cause gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
(stomach flu). A combination of conjunctivitis and tonsilitis is particularly common with adenovirus infections. Some children (especially small ones) can develop adenovirus bronchiolitis
Bronchiolitis
Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It usually occurs in children less than two years of age and presents with coughing, wheezing, and shortness of breath. This inflammation is usually caused by viruses...
or pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
, both of which can be severe. In babies, adenoviruses can also cause coughing fits that look almost exactly like whooping cough. Adenoviruses can also cause viral meningitis
Viral meningitis
Viral meningitis refers to meningitis caused by a viral infection. It is sometimes referred to as "aseptic meningitis" in contrast to meningitis caused by bacteria.An example is lymphocytic choriomeningitis....
or encephalitis
Encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...
. Rarely, adenovirus can cause hemorrhagic cystitis
Hemorrhagic cystitis
Hemorrhagic cystitis or Haemorrhagic cystitis is diffuse inflammation of the bladder leading to dysuria, hematuria, and hemorrhage. The disease can occur as a complication of cyclophosphamide, ifosfamide and radiation therapy...
(inflammation of the urinary bladder—a form of urinary tract infection
Urinary tract infection
A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...
— with blood in the urine).
Most people recover from adenovirus infections by themselves, but people with immunodeficiency
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...
sometimes die of adenovirus infections, and — rarely — even previously healthy people can die of these infections.
Adenoviruses are often transmitted by expectorate, but can also be transmitted by contact with an infected person, or by virus particles left on objects such as towels and faucet handles. Some people with adenovirus gastroenteritis may shed the virus in their stools for months after getting over the symptoms. The virus can be passed from one person to another through some sexual practices, and through water in swimming pools that do not have enough chlorine in them. As with many other illnesses, good handwashing is one way to lessen the spread of adenoviruses from one person to another. Heat and bleach
Bleach
Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...
will kill adenoviruses on objects.
Treatment
There are no antiviral drugs to treat adenoviral infections, so treatment is largely directed at the symptoms (such as acetaminophen for fever). A doctor may give antibiotic eyedrops for conjunctivitis, since it takes a while to test to see if the eye infection is bacterial or viral and to help prevent secondary bacterial infections.Utilization in treatment of unrelated diseases
Adenovirus is used as a vehicle to administer targeted therapyTargeted therapy
Targeted therapy is a type of medication that blocks the growth of cancer cells by interfering with specific targeted molecules needed for carcinogenesis and tumor growth, rather than by simply interfering with rapidly dividing cells...
, in the form of recombinant DNA
Recombinant DNA
Recombinant DNA molecules are DNA sequences that result from the use of laboratory methods to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in biological organisms...
or protein. Specific modifications on fibre proteins are used to target Adenovirus to certain cell types; a major effort is made to limit hepatotoxicity
Hepatotoxicity
Hepatotoxicity implies chemical-driven liver damage.The liver plays a central role in transforming and clearing chemicals and is susceptible to the toxicity from these agents. Certain medicinal agents, when taken in overdoses and sometimes even when introduced within therapeutic ranges, may injure...
and prevent multiple organ failure. Adenovirus dodecahedron can qualify as a potent delivery platform for foreign antigens to human myeloid dendritic cells (MDC), and that it is efficiently presented by MDC to M1-specific CD8+ T lymphocytes.
External links
- Centers for Disease Control and Prevention--National Center for Diseases--Division of Viral and Rickettsial Diseases, Respiratory and Enteric Viruses Branch
- MicrobiologyBytes: Adenoviruses
- Stanford University - Adenoviruses
- Adenoviruses General Concepts
- DNA virus replication strategies
- Sequenced adenoviruses
- Kids Health - Adenoviruses
- Viralzone: Adenoviridae
- Adenovirus Research Discussion Group
- USAMRMC protects Soldiers against unseen enemy